Is this a hard mod (chip, tsop flash) or a soft mod? If the former, just boot off a burned DVD and reload the MS Dash files via FTP. Or just reload the dash of your choice from Slayer's or AID. If the latter, then it's a bit more involved. Your best course of action will be to remove the hard drive from the system after it has booted (so the hard drive is unlocked) and then connect it to a PC and restore the backup you made when you first soft modded.
